Base station, terminal, band allocation method, and downlink data communication method

ABSTRACT

Provided are a base station, a terminal, a band allocation method, and a downlink data communication method in which a mapping method for synchronization signals and report signals is implemented with high resource usage efficiency when a first system in which an independent single communication is allocated to a unit band co-exists with a second system in which a plurality of unit bands can be allocated to a single communication. In a base station, an OFDM signal generation unit maps primary synchronization channel (P-SCH), secondary synchronization channel (S-SCH), primary broadcast channel (P-BCH), and dynamic broadcast channel (D-BCH), which can be decoded by both an LTE terminal and an LTE+ terminal, to some of a plurality of unit bands. The OFDM signal generation unit also maps D-BCH+, which can be decoded only by an LTE+ terminal, to all of the plurality of unit bands to produce a multiplexed transmission signal.

BACKGROUND

1. Technical Field

The present invention relates to a base station, terminal, bandassignment method and downlink data communication method.

2. Description of the Related Art

In 3GPP LTE, OFDMA (Orthogonal Frequency Division Multiple Access) isadopted as a downlink communication scheme. In a radio communicationsystem adopting 3GPP LTE, a radio communication base station apparatus(which may be simply referred to as “base station” below) transmits asynchronization channel (“SCH”) or broadcast channel (“BCH”) usingpredetermined communication resources. Then, first, a radiocommunication terminal apparatus (which may be simply referred to as“terminal” below) maintains synchronization with the base station byreceiving the SCH. That is, first, the terminal performs a cell search.After that, the terminal obtains parameters unique to the base station(such as a frequency bandwidth) by reading the BCH information (seeNon-Patent Literatures 1, 2 and 3).

Also, standardization of 3GPP LTE-advanced, which realizes fastercommunication than 3GPP LTE, has been started. The 3GPP LTE-advancedsystem (which may be referred to as “LTE+ system” below) follows the3GPP LTE system (which may be referred to as “LTE system” below). In3GPP LTE-advanced, to realize the downlink transmission speed equal toor greater than maximum 1 Gbps, it is expected to adopt a base stationand terminal that can perform communication in a wideband frequencyequal to or greater than 20 MHz. Here, to prevent unnecessarycomplication of the terminal, the terminal side is expected to definethe terminal capability related to frequency band support. The terminalcapability defines that, for example, the minimum value of supportbandwidth is 20 MHz.

CITATION LIST Non-Patent Literature

[NPL 1]

3GPP TS 36.211 V8.3.0, “Physical Channels and Modulation (Release 8),”May 2008

[NPL 2]

3GPP TS 36.212 V8.3.0, “Multiplexing and channel coding (Release 8),”May 2008

[NPL 3]

3GPP TS 36,213 V8.3.0, “Physical layer procedures (Release 8),” May 2008

BRIEF SUMMARY Technical Problem

Here, a case is assumed where a base station supporting an LTE+ system(which may be referred to as “LTE+ base station”) supports a terminalsupporting an LTE system (which may be referred to as “LTE terminal”).Also, the LTE+ base station is formed to be able to performcommunication in a frequency band including a plurality of “unit bands.”Here, a “unit band” is a band of a 20-MHz range including SCH(Synchronization CHannel) near the center and is defined as a base unitof a communication band. Also, a “unit band” may be expressed as“component carrier(s)” in English in 3GPP LTE.

FIG. 1 shows an example of mapping SCH and BCH in the LTE+ systemsupport base station.

In FIG. 1, a communication bandwidth of the LTE+ base station is 60 MHzand includes three unit bands. Also, SCH and BCH, which cannot beinterpreted by an LTE terminal, are placed at 20 MHz intervals near thecenter frequency of each unit band. Also, a physical downlink controlchannel (PDCCH) is placed over each unit band in a distributed manner.

By adopting such a mapping method, an LTE terminal of only 20-MHzterminal capability can find synchronization with the LTE+ base stationif this terminal camps in any unit band, and start communication byreading a BCH. Also, a unit band with which synchronization is foundbetween the terminal and the base station may be referred to as “initialaccess unit band.” Also, a BCH includes frequency band information,which divides a communication band every unit band. In view of theabove, a unit band is also defined as a band divided using frequencyband information in a BCH or a band defined by a distribution width uponplacing a PDCCH in a distributed manner.

By the way, an LTE+ base station needs to support an LTE+ system supportterminal (which may be referred to as “LTE+ terminal” below) in additionto the above LTE terminal. Similar to the LTE terminal, the LTE+terminal includes a terminal having terminal capability of only the samecommunication bandwidth as a unit band, and a terminal having terminalcapability of a communication bandwidth combining a plurality of unitbands.

That is, actually, an integrated communication system including the LTEsystem in which single communication is independently assigned everyunit band and the LTE+ system which follows the LTE system and in whicha plurality of unit bands can be assigned in single communication.

In this integrated communication system, the LTE+ base station needs tomap a synchronization signal and broadcast signal which can beinterpreted by both an LTE terminal and LTE+ terminal (i.e., LTEsynchronization signal and LTE broadcast signal), and a synchronizationsignal and broadcast signal which cannot be interpreted by the LTEterminal and which are required for the LTE+ terminal (i.e., LTE+synchronization signal and LTE+ broadcast signal), on the support band.

However, a method of mapping a synchronization signal and broadcastsignal in such a new integrated communication system is not proposedyet.

It is therefore an object of the present invention to provide a basestation, terminal, band assignment method and downlink datacommunication method for realizing a method of mapping synchronizationsignals and broadcast signals having high use efficiency of resources,in a case where there are a first system in which single communicationis independently assigned every unit band having a predeterminedbandwidth and a second system which follows the first system and inwhich a plurality of unit bands can be assigned in single communication.

Solution to Problem

The base station of the present invention representing a second-systemsupport base station in an integrated communication system including afirst system in which single communication is independently assignedevery unit band having a predetermined bandwidth and a second system inwhich single communication can be assigned a plurality of unit bands,employs a configuration having: a forming section that forms a multiplexsignal by mapping a synchronization channel, first-system broadcastsignal and first-system dynamic broadcast signal, which can beinterpreted by a first-system support terminal and second-system supportterminal, on part of the plurality of unit bands that can be used by thebase station, and mapping a second-system dynamic broadcast signal thatcan be interpreted only by the second-system support terminal on all ofthe plurality of unit bands; and a transmission section that transmitsthe multiplex signal.

The terminal of the present invention representing a second-systemsupport terminal that receives a data signal transmitted from the abovebase station in a destination unit band corresponding to a band movingindication transmitted from the base station, employs a configurationhaving: a receiving section that receives a second-system dynamicbroadcast signal; and a control section that makes the receiving sectionstart reception processing of the second-system dynamic broadcast signalafter a start of reception processing of the data signal.

The band assignment method of the present invention whereby asecond-system support base station assigns a used unit band for use indata communication to a second-system support terminal, in an integratedcommunication system including a first system in which singlecommunication is independently assigned every unit band having apredetermined bandwidth and a second system in which singlecommunication can be assigned a plurality of unit bands, includes thesteps of: in an assignment target terminal, sequentially shifting areception band and searching for a synchronization channel, which isassigned to a predetermined frequency and transmitted from thesecond-system support base station and which can be interpreted by afirst-system support terminal and the second-system support terminal; inthe assignment target terminal, receiving a first-system broadcastsignal, a control channel and a first-system dynamic broadcast signaland preparing a preamble transmission of random access channel, wherethe first-system broadcast signal, the control channel and the controlchannel and the first-system dynamic broadcast signal are transmittedfrom the second-system support base station in an initial access unitband including the searched frequency position of the synchronizationchannel and can be interpreted by the first-system support terminal andthe second-system support terminal; transmitting the preamble of randomaccess channel using a resource corresponding to random access channelresource information included in the first-system dynamic broadcastsignal and transmitted from the second-system support base station; inthe second-system support base station, reporting resource allocationinformation to the assignment target terminal in the control channelupon receiving the preamble of random access channel; in the assignmenttarget terminal, reporting terminal capability information of theterminal to the second-system support base station using a resourceindicated by the resource allocation information; and in thesecond-system support base station, when the terminal capabilityinformation indicates the second-system support terminal, assigning aunit band different from the initial access unit band as the used unitband and commanding the reception band to be moved by transmitting theassignment information to the assignment target terminal.

The downlink data communication method of the present inventionincluding the above band assignment method, includes: starting a datareception in the destination unit band after the assignment targetterminal moves the reception band to the destination unit band; and, inthe assignment target terminal that started the data reception,receiving a control channel transmitted from the second-system supportbase station in the destination unit band and a second-system dynamicbroadcast signal that can be received based on the control channel.

Advantageous Effects of Invention

According to the present invention, it is possible to a base station,terminal, band assignment method and downlink data communication methodfor realizing a method of mapping synchronization signals and broadcastsignals having high use efficiency of resources, in a case where thereare a first system in which single communication is independentlyassigned every unit band having a predetermined bandwidth and a secondsystem in which single communication can be assigned a plurality of unitbands.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of mapping an SCH and BCH in an LTE+ systemsupport base station;

FIG. 2 shows an example of mapping an SCH and BCH in an LTE+ systemsupport base station;

FIG. 3 is a conceptual diagram in which an LTE+ base station supporting60 MHz transmits an SCH and BCH only in part of unit bands;

FIG. 4 is a block diagram showing a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 5 is a block diagram showing a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 6 illustrates a method of mapping a synchronization signal,broadcast signal and control channel in the base station according toEmbodiment 1 of the present invention;

FIG. 7 is a sequence diagram showing signal transmission and receptionbetween a terminal and base station;

FIG. 8 illustrates a method of mapping a synchronization signal,broadcast signal and control channel in a base station according toEmbodiment 2 of the present invention; and

FIG. 9 illustrates operational explanation of a terminal according toEmbodiment 2 of the present invention.

DETAILED DESCRIPTION

As described above, an LTE+ base station needs to support an LTEterminal and therefore transmits a primary SCH (“P-SCH”), secondary SCH(“S-SCH”), primary BCH (“P-BCH”) and dynamic BCH (“D-BCH”) used in theLTE terminal, according to the LTE standard. Here, the P-SCH and S-SCHcorrespond to a first system synchronization signal, the P-BCHcorresponds to a first-system broadcast signal, and the D-BCHcorresponds to a first-system dynamic broadcast signal.

Further, the LTE+ base station needs to support an LTE+ terminal too.Therefore, the LTE+ base station needs to transmit a primarySCH+(“PSCH+”), secondary SCH+ (“S-SCH+”), primary BCH+ (“P-BCH+”) anddynamic BCH+ (“D-BCH+”) used in the LTE+ terminal. Here, the P-SCH+ andS-SCH+ corresponds to a second system synchronization signal, the P-BCH+corresponds to a second system broadcast signal and the D-BCH+corresponds to a second system dynamic signal.

Therefore, first, the present inventors have thought of a mapping methodfor mapping an SCH+ and BCH+ on the mapping frequency for SCH's andBCH's shown in FIG. 1 (see FIG. 2).

According to the mapping method shown in FIG. 2, an LTE terminal and anLTE+ terminal having 20-MHz terminal capability can receive an SCH andBCH (SCH+ and BCH+) in all bands. Therefore, the LTE terminal and LTE+terminal can be present at the same time in all bands, so that it isexpected to smooth the data traffic in an integrated communicationsystem.

However, as clear from FIG. 2, compared to the LTE system, downlinkresources used for SCH and BCH transmission increases, and,consequently, the use efficiency of resources degrades.

Therefore, to improve the use efficiency of resources, a method isproposed to map an SCH and BCH (SCH+ and BCH+) on only a part of unitbands included in the communication band of the LTE+ terminal.

FIG. 3 is a conceptual diagram of transmitting an SCH and BCH only inpart of unit bands in an LTE+ base station supporting 60 MHz. Here, anSCH and BCH are transmitted only in the center unit band (unit band 2 inFIG. 3) among a plurality of unit bands included in the communicationband of the LTE+ terminal. By this means, resources required to transmitan SCH and BCH are reduced.

However, in this case, a terminal supporting up to 20 MHz (including anLTE terminal and LTE+ terminal) cannot access unit band 1 and unit band3. Consequently, if the number of LTE+ terminals supporting 40 MHz or 60MHz is small, unit bands at both ends may not be used, and a problemarises that the use efficiency of resources is degraded.

After recognizing the above problems, first, an LTE+ terminal also needsto access an LTE base station, the present inventors focus on the factthat the LTE+ terminal has capability of receiving an SCH and BCH for anLTE terminal.

Further, the present inventors focus on the fact that, when the singleLTE+ base station supports an LTE terminal and LTE+ terminal, thecontent of broadcast signals related to the system in each unit band(e.g., the number of antenna ports, system band, and so on) is verysimilar.

Focusing the above points, the present inventors have arrived at thepresent invention.

Now, embodiments of the present invention will be explained in detailwith reference to the accompanying drawings. Also, in embodiments, thesame components will be assigned the same reference numerals and theiroverlapping explanation will be omitted.

Embodiment 1

The communication system according to Embodiment 1 of the presentinvention is the integrated communication system including a firstsystem in which single communication is independently assigned everyunit band having a predetermined bandwidth and a second system whichfollows the first system and in which a plurality of unit bands can beassigned in single communication. An example case will be explainedbelow where the first system is an LTE system and a second system is anLTE+ system.

[Terminal Configuration]

FIG. 4 is a block diagram showing a configuration of terminal 100according to Embodiment 1 of the present invention. Terminal 100represents an LTE+ terminal. In FIG. 4, terminal 100 is provided with RFreceiving section 105, OFDM signal demodulating section 110, framesynchronization section 115, demultiplexing section 120, broadcastinformation receiving section 125, PDCCH receiving section 130, PDSCH(Physical Downlink Shared CHannel) receiving section 135, controlsection 140, RACH (Random Access CHannel) preamble section 145,modulating section 150, SC-FDMA (Single-Carrier Frequency DivisionMultiple Access) signal forming section 155 and RF transmission section160.

RF receiving section 105 is formed to be able to change a receptionband. RF receiving section 105 receives a center frequency indicationfrom control section 140 and, by moving the center frequency based onthis center frequency indication, moves the reception band. RF receivingsection 105 performs radio reception processing (such as down-conversionand analog-to-digital (A/D) conversion) on a radio reception signalreceived in the reception band via an antenna, and outputs the resultingreception signal to OFDM signal demodulating section 110. Also, here,although the center frequency of the reception band is used as a basefrequency, it is equally possible to use an arbitrary frequency includedin the reception band as the base frequency.

OFDM signal demodulating section 110 has CP (Cyclic Prefix) removingsection 111 and fast Fourier Transform (FFT) section 112. OFDM signaldemodulating section 110 receives the reception OFDM signal from RFreceiving section 105. In OFDM signal demodulating section 110, CPremoving section 111 removes a CP from the reception OFDM signal and FFTsection 112 transforms the reception OFDM signal without a CP into afrequency domain signal. This frequency domain signal is outputted toframe synchronization section 115.

Frame synchronization section 115 searches for a synchronization signal(SCH) included in the signal received from OFDM signal demodulatingsection 110 and finds synchronization with base station 200 (describedlater). A unit band included in the found synchronization signal (SCH)is used as the initial access unit band. The synchronization signalincludes a P-SCH (Primary SCH) and S-SCH (Secondary SCH). To be morespecific, frame synchronization section 115 searches for the P-SCH andfinds synchronization with base station 200 (described later).

After finding the P-SCH, frame synchronization section 115 performsblind detection of the S-SCH placed in resources having a predeterminedrelationship with resources in which the P-SCH is placed. By this means,it is possible to find more precise synchronization and obtain the cellID associated with the S-SCH sequence. That is, frame synchronizationsection 115 performs the same processing as in a normal cell search.

Frame synchronization section 115 outputs frame synchronization timinginformation related to the synchronization establishment timing, todemultiplexing section 120.

Demultiplexing section 120 demultiplexes the reception signal receivedfrom OFDM signal demodulating section 110 into the broadcast signal,control signal (i.e., PDCCH signal) and data signal (i.e., PDSCH signal)included in this reception signal, based on the frame synchronizationtiming information. The broadcast signal is outputted to broadcastinformation receiving section 125, the PDCCH signal is outputted toPDCCH receiving section 130, and the PDSCH signal is outputted to PDSCHreceiving section 135. Here, the PDSCH includes individual informationfor a given terminal.

Broadcast information receiving section 125 reads the content of theinput P-BCH and obtains information related to the number of antennas ofbase station 200 (described later) and downlink system bandwidth. Thisinformation is outputted to control section 140.

Broadcast information receiving section 125 receives a D-BCH signalplaced in resources indicated by D-BCH (Dynamic BCH) resource positioninformation (D-BCH frequency position information in this case) includedin the PDCCH signal and extracted in PDCCH receiving section 130, andobtains information included in this received D-BCH signal (e.g.,information about the frequency and frequency band of uplink pair bandor PRACH (Physical Random Access CHannel)). This information isoutputted to control section 140. Also, in this specification, anexample case will be explained using frequency as resources.

Based on the frequency position related to the decoding indication fromcontrol section 140, PDCCH receiving section 130 extracts information(including the frequency position in which the D-BCH and D-BCH+ areplaced, the frequency position in which the PDSCH is placed, and uplinkfrequency allocation information (PUSCH frequency position informationin this case)), included in the PDCCH signal received fromdemultiplexing section 120. Out of this extracted information, the D-BCHand D-BCH+are outputted to broadcast information receiving section 125,information of the frequency position in which the PDSCH is placed isoutputted to PDSCH receiving section 135, and the uplink frequencyallocation information is outputted to SC-FDMA signal forming section155. Here, the information of the frequency position in which the D-BCHis placed and the information of the frequency position in which thePDSCH is placed are extracted before RACH preamble transmission, theuplink frequency allocation information is outputted after RACH preambletransmission, and the information of the frequency position in which theD-BCH+ is placed is extracted after the start of data signal reception.That is, only the information of the frequency position in which theD-BCH+ is placed is extracted in the destination unit band, and the restof the information is extracted in the initial access unit band.

PDSCH receiving section 135 extracts a band moving indication from thePDSCH signal received from demultiplexing section 120, based on theinformation about the frequency position in which the PDSCH is placed,received from PDCCH receiving section 130. Then, the extracted bandmoving indication is outputted to control section 140.

Here, the band moving indication includes all information required tostart communication in the destination unit band. The band movingindication includes, for example, information about the destination unitband and pair uplink bands, the center frequency of the destination unitband (which corresponds to the center frequency of a PDCCH for the LTE+terminal), and information required for reading a PDCCH and PDSCH in thedestination unit band (i.e., information of the frequency position inwhich the PDCCH and PDSCH are placed). Here, in order to reduce thesignaling amount required for the band moving indication, the centerfrequency of the destination unit band to adjust in RF receiving section105 of the LTE+ terminal is reported as a multiple of 300 KHz, which isthe lowest common multiple of the downlink subcarrier bandwidth (15 KHz)and the minimum resolution of frequency that can be set by RF receivingsection 105 of terminal 100 (100 KHz). This is because, when an LTE+base station transmits a plurality of SCH's using one IFFT circuit, theinterval between SCH's is nothing but an integral multiple of 15 KHz,and, furthermore, needs to be a multiple of 100 KHz to adjust the centerfrequency of a reception band for any SCH on the terminal side.

Control section 140 sequentially changes the reception band of RFreceiving section 105 before synchronization is established. Also,control section 140 prepares RACH preamble transmission, based on theLTE broadcast signal, control channel and LTE dynamic broadcast signalwhich can be interpreted by the LTE terminal and LTE+ terminal and whichare transmitted from base station 200 (described later) in the initialaccess unit band including the frequency position of the synchronizationchannel after synchronization is established and before an RACH preambleis transmitted. Also, after RACH preamble transmission, control section140 obtains report resource assignment information reported by thecontrol channel from base station 200 (described later), transmitsterminal capability information of that terminal using resourcesindicated by that report resource assignment information, and, based ona band moving indication transmitted from base station 200 according tothe terminal capacity information, changes the reception band from theinitial access unit band to the unit band in use.

To be more specific, control section 140 identifies PDCCH placementinformation based on the information obtained in broadcast informationreceiving section 125. This PDCCH placement information is uniquelydetermined by the number of antennas and downlink system bandwidth ofbase station 200 (described later). Control section 140 outputs thePDCCH placement information to PDCCH receiving section 130 and commandsdecoding of a signal placed in the frequency position according to thatinformation.

Also, control section 140 commands RACH preamble section 145 to transmitan RACH preamble according to information included in the D-BCH signalreceived from broadcast information receiving section 125, that is,according to the uplink frequency band and PRACH frequency position.

Also, upon receiving the uplink frequency allocation information fromPDCCH receiving section 130, control section 140 outputs terminalcapability information (i.e., capability information) of that terminalto modulating section 150 and outputs the uplink frequency allocationinformation to SC-FDMA signal forming section 155. By this means, theterminal capability information is mapped on frequency corresponding tothe uplink frequency allocation information and then transmitted.

Also, based on the band moving indication received from PDSCH receivingsection 135, control section 140 outputs a center frequency indicationto RF receiving section 105 such that the reception band of RF receivingsection 105 matches the destination band. Here, upon performing movecontrol of the reception band based on that band moving indication,control section 140 outputs a decoding indication to PDCCH receivingsection 130. By this means, PDCCH receiving section 130 can receive thePDCCH signal in the destination unit band. By specifying frequency inwhich the D-BCH+ is placed from the PDCCH signal in that destinationunit band, broadcast information receiving section 125 can receive theD-BCH+ placed in the destination unit band. Then, the decodingindication is outputted after the start of data signal reception inPDSCH receiving section 135.

Also, when sequential data communication with base station 200(described later) is finished (i.e., when there is no data to transmitto the sides of base station 200 and terminal 100), control section 140switches the mode of terminal 100 to an idle mode. At this time, controlsection 140 moves the reception band of terminal 100 from thedestination unit band to the initial access unit band. By this means,terminal 100 can receive an SCH and BCH even in the idle mode, so thatit is possible to start new communication smoothly.

According to the indication from control section 140, RACH preamblesection 145 outputs an RACH preamble sequence and information related tothe uplink frequency band and PRACH frequency position included in thatindication, to SC-FDMA signal forming section 155.

Modulating section 150 modulates the terminal capability informationreceived from control section 140 and outputs the resulting modulationsignal to SC-FDMA signal forming section 155.

SC-FDMA signal forming section 155 forms an SC-FDMA signal from themodulation signal received from modulating section 150 and the RACHpreamble sequence received from RACH preamble section 145. In SC-FDMAsignal forming section 155, discrete Fourier transform (DFT) section 156transforms the input modulation signal on the frequency axis and outputsa plurality of resulting frequency components to frequency mappingsection 157. These plurality of frequency components are mapped onfrequency based on the uplink frequency allocation information infrequency mapping section 157 and transformed into a time domainwaveform in IFFT section 158. The RACH preamble sequence is also mappedon frequency based on the uplink frequency allocation information infrequency mapping section 157 and transformed into a time domainwaveform in IFFT section 158. CP attaching section 159 attaches a CP tothe time domain waveform and provides an SC-FDMA signal.

RF transmission section 160 performs radio transmission processing onthe SC-FDMA signal formed in SC-FDMA signal forming section 155 andtransmits the result via an antenna.

[Base station configuration] FIG. 5 is a block diagram showing aconfiguration of base station 200 according to Embodiment 1 of thepresent invention. Base station 200 is an LTE+ base station. Basestation 200 always continues to transmit a P-SCH, S-SCH, P-BCH, D-BCH,D-BCH+, PDCCH representing D-BCH frequency scheduling information andPDCCH representing D-BCH+ frequency scheduling information, in an OFDMscheme.

In FIG. 5, base station 200 is provided with PDCCH generating section205, PDSCH generating section 210, broadcast signal generating section215, modulating section 220, OFDM signal forming section 225, RFtransmission section 230, RF receiving section 235, CP removing section240, FFT section 245, extracting section 250, RACH preamble receivingsection 255, data receiving section 260 and control section 265. CPremoving section 240, FFT section 245, extracting section 250, RACHpreamble receiving section 255 and data receiving section 260 form anSC-FDMA signal demodulating section.

PDSCH generating section 205 receives uplink frequency allocationinformation for terminal 100 and generates a PDCCH signal including thisuplink frequency allocation information. PDCCH generating section 205masks the uplink frequency allocation information by CRC based on anRACH preamble sequence transmitted from terminal 100, and then includesthe result in the PDCCH signal. The generated PDCCH signal is outputtedto modulating section 220. Here, a sufficient number of RACH preamblesequences are prepared, and the terminal selects an arbitrary sequencefrom these RACH preamble sequences and accesses the base station. Thatis, there is an extremely low possibility that a plurality of terminalsaccess base station 200 at the same time using the same RACH preamblesequence, so that, by receiving a PDCCH subjected to CRC masking basedon that RACH preamble sequence, terminal 100 can detect uplink frequencyallocation information for that terminal without problems.

PDSCH generating section 210 receives a band moving indication fromcontrol section 265 and generates a PDSCH signal including this bandmoving indication. Also, PDSCH generating section 210 receives as inputtransmission data after transmission of the band moving indication.Then, PDSCH generating section 210 generates a PDSCH signal includingthe input transmission data. The PDSCH signal generated in PDSCHgenerating section 210 is received as input in modulating section 220.

Broadcast signal generating section 215 generates and outputs abroadcast signal to modulating section 220. This broadcast signalincludes a P-BCH, D-BCH and D-BCH+.

Modulating section 220 forms modulation signals by modulating inputsignals. These input signals represent the PDCCH signal, PDSCH signaland broadcast signal. The formed modulation signals are received asinput in OFDM signal forming section 225.

OFDM signal forming section 225 receives as input the modulation signalsand synchronization signals (P-SCH and S-SCH) and forms an OFDM signalin which those signals are mapped on predetermined resources,respectively. In OFDM signal forming section 225, multiplexing section226 multiplexes the modulation signals and the synchronization signals,and IFFT section 227 obtains a time domain waveform by performingserial-to-parallel conversion and then performing an IFFT of themultiplex signal. By attaching a CP to this time domain waveform in CPattaching section 228, the OFDM signal is provided.

RF transmission section 230 performs radio transmission processing onthe OFDM signal formed in OFDM signal forming section 225 and transmitsthe result via an antenna.

RF receiving section 235 performs radio reception processing (such asdown-conversion and analog-to-digital (A/D) conversion) on a radioreception signal received in a reception band via the antenna, andoutputs the resulting reception signal to CP removing section 240.

CP removing section 240 removes a CP from the reception SC-FDMA signaland FFT section 245 transforms the reception SC-FDMA signal without a CPinto a frequency domain signal.

Extracting section 250 extracts a signal mapped on resourcescorresponding to the RACH, from the frequency domain signal receivedfrom FFT section 245, and outputs the extracted signal to RACH preamblereceiving section 255. This extraction of the signal mapped on theresources corresponding to the RACH is always performed so that an LTE+terminal transmits an RACH preamble to base station 200 at any timing.

Also, extracting section 250 extracts a signal corresponding to uplinkfrequency allocation information received from control section 265, andoutputs this signal to data receiving section 260. This extracted signalincludes, for example, terminal capability information transmitted byterminal 100 in a PUSCH.

First, RACH preamble receiving section 255 transforms the extractedsignal received from extracting section 250 into a single carriersignal. That is, RACH preamble receiving section 255 includes an inversediscrete Fourier transform (IDFT) circuit. Then, RACH preamble receivingsection 255 finds correlation between the resulting single carriersignal and an RACH preamble pattern, and, if the correlation value isequal to or greater than a certain level, decides that an RACH preambleis detected. Then, RACH preamble receiving section 255 outputs an RACHdetection report including pattern information of the detected RACHpreamble (e.g., the sequence number of the RACH preamble) to controlsection 265.

Data receiving section 260 transforms the extracted signal received fromextracting section 250 into a single carrier signal on the time axis andoutputs terminal capability information included in the resulting singlecarrier signal to control section 265. Also, after transmission of theband moving indication, data receiving section 260 outputs the resultingsingle carrier signal to a higher layer as reception data.

Upon receiving the RACH detection report from RACH preamble receivingsection 255, control section 265 allocates uplink frequency to terminal100 having transmitted the detected RACH preamble. This allocated uplinkfrequency is used to, for example, transmit terminal capabilityinformation in terminal 100. Then, the uplink frequency allocationinformation is outputted to PDCCH generating section 205.

Also, upon receiving the terminal capability information from datareceiving section 260, control section 265 decides whether thetransmission source terminal is the LTE terminal or the transmissionsource terminal is the LTE+ terminal, based on the terminal capabilityinformation. If it is decided as the LTE+ terminal, control section 265forms a band moving indication for this LTE+ terminal and outputs thisband moving indication to PDSCH generating section 210. The band movingindication is formed depending on the density condition in each band.Here, as described above, this band moving indication includesinformation about the difference from the center frequency position inthe RF receiving section of the terminal. This difference informationhas the value that is an integral multiple of 300 KHz. Also, the bandmoving indication includes PDCCH and PDSCH placement positioninformation in the destination unit band. Similar to normal downlinkdata, the band moving indication is prepared for each terminal in PDSCHgenerating section 210 and then received as input in the modulatingsection.

Also, after outputting the band moving indication, control section 265controls the PDCCH and PDSCH for the terminal subject to that indicationto be placed in the destination unit band.

Also, after finishing sequential data communication with terminal 100(i.e., after there is no data to transmit to the sides of base station200 and terminal 100), in a case where some data needs to be transmittedto terminal 100, control section 265 performs transmission using theinitial access unit band. This is because, after the end of sequentialdata communication, terminal 100 is in an idle state by moving thereception band from the destination unit band to the initial access unitband.

[Operations of Terminal 100 and Base Station 200]

[Method of Mapping a Synchronization Signal, Broadcast Signal andControl Channel]

FIG. 6 illustrates a method of mapping a synchronization signal,broadcast signal and control channel in base station 200. Base station200 transmits a synchronization signal, broadcast signal and controlchannel in the mapping method as shown in FIG. 6.

As shown in FIG. 6, base station 200 provides a plurality of unit bandsin the communication band. Here, among the plurality of unit bands, aP-SCH, S-SCH, P-BCH and D-BCH, which can be interpreted by an LTEterminal and LTE+ terminal, are mapped only on part of the unit bands.Further, a D-BCH+ that can be interpreted only by the LTE+ terminal ismapped on all of the plurality of unit bands. Also, the frequencyposition on which the P-SCH and S-SCH are mapped is the center frequencyor near the center frequency of the unit band on which the P-SCH andS-SCH are mapped.

This mapping method represents a mapping method with higher useefficiency of resources than the mapping method shown in FIG. 2. Also, acontrol channel (PDCCH) indicating frequency position information of theP-SCH, S-SCH, P-BCH, D-BCH and D-BCH+ is always repeatedly transmitted.

(Signal Transmission and Reception Between Terminal 100 and Base Station200)

FIG. 7 is a sequence diagram showing signal transmission and receptionbetween terminal 100 and base station 200.

In steps S1001 and S1002, a synchronization signal is transmitted, andcell search processing is performed using this synchronization signal.That is, in step S1001, the reception band of RF receiving section 105is sequentially shifted by control of control section 140, and framesynchronization section 115 searches for a P-SCH. By this means, theinitial synchronization is established. Then, in step S1002, framesynchronization section 115 performs blind detection of an S-SCH placedin resources having a predetermined relationship with resources in whichthe P-SCH is placed. By this means, it is possible to find more precisesynchronization and obtain the cell ID associated with the S-SCHsequence.

In step S1003 to step S1005, a broadcast signal and control channel aretransmitted and used to prepare RACH preamble transmission.

That is, in step S1003, control section 140 identifies PDCCH placementinformation based on information included in a received D-BCH signal andobtained in broadcast information receiving section 125 (e.g.,information about frequency and frequency band of uplink pair band orPRACH (Physical Random Access CHannel)). Then, control section 140outputs the PDCCH placement information to PDCCH receiving section 130and commands decoding of a signal placed in the frequency position basedon the information.

In step S1004, according to the decoding indication from control section140, frequency position information of the D-BCH is extracted in PDCCHreceiving section 130.

In step S1005, based on the D-BCH frequency position information,information included in the received D-BCH signal (e.g., informationabout frequency and frequency band of uplink pair band or PRACH(Physical Random Access CHannel)) is extracted in broadcast informationreceiving section 125.

In step S1006, under control of control section 140, RACH preamblesection 145 transmits an RACH preamble using the uplink frequency bandand PRACH frequency position obtained in step S1003.

In step S1007, control section 265 of base station 200 having receivedthe RACH preamble allocates uplink frequency to terminal 100 havingtransmitted the RACH preamble, and transmits uplink frequency allocationinformation to that terminal 100.

In step S1008, control section 140 of terminal 100 having received theuplink frequency allocation information transmits terminal capabilityinformation of that terminal, using the uplink frequency.

In step S1009, if the received terminal capability indicates the LTE+terminal, control section 265 transmits a band moving indication.

Terminal 100, having received this band moving indication, shifts thereception band to a unit band indicated by the band moving indicationand starts data communication.

In step S1010, control section 140 issues a decoding indication to PDCCHreceiving section 130 based on PDCCH position information of thedestination unit band, and PDCCH receiving section 130 obtains D-BCH+frequency position information according to this indication.

In step S1011, broadcast information receiving section 125 extractsinformation included in the received D-BCH+ based on the D-BCH+frequency position information.

Here, the above band moving indication includes all information requiredto read the PDCCH in the destination unit band. Therefore, terminal 100as the LTE+ terminal needs to read the content of the D-BCH+ to startdata communication in the destination unit band.

However, the D-BCH includes information whose parameter content changesdepending on the number of terminals that communicate with the basestation, such as information related to power control and information ofa slot in which it is possible to transmit a sounding reference used toobtain uplink channel information, in addition to information requiredto start communication.

Such information needs to be read during communication (i.e., activestate (which is a state where terminal 100 continues to receive a PDCCHfrom base station 200 in each subframe)) in terminal 100. Therefore,base station 200 transmits the D-BCH+ including only informationrequired for communication. That is, information that needs not be readby terminal 100 in the active state is reduced, so that it is possibleto reduce the size of the D-BCH+. That is, the overhead of resources isreduced.

As described above, according to the present embodiment, in base station200 as an LTE+ base station, OFDM signal forming section 225 forms atransmission multiplex signal by mapping a P-SCH, S-SCH, P-BCH andD-BCH, which can be interpreted by an LTE terminal and LTE+ terminal, onpart of a plurality of unit bands that can be used by that base station,and mapping a D-BCH+ that can be interpreted only by the LTE+ terminalon all of the plurality of unit bands.

By this means, it is possible to transmit a synchronization signal andbroadcast signal required for the LTE terminal and LTE+ terminal in amapping method having high use efficiency of resources.

Also, in base station 200, if a terminal having transmitted terminalcapability information is an LTE+ terminal, control section 265transmits a band moving indication indicating a change of the receptionband, to that terminal. By contrast with this, in terminal 100, controlsection 265 changes the reception band from the initial access unit bandto a unit band corresponding to the band moving indication.

By this means, it is possible to equalize the number of terminals thatperform communication in each unit band, between unit bands. That is,according to the above mapping method, an LTE terminal accesses onlypart of the unit bands (i.e., a unit band on which a P-SCH, S-SCH, P-BCHand D-BCH are mapped), and, consequently, LTE terminals tend to beconcentrated in that part of the unit bands. Therefore, by shifting thereception band of the LTE+ terminal to a unit band different from theunit band on which the P-SCH, S-SCH, P-BCH and D-BCH are mapped, it ispossible to sort terminals into each band in a balanced manner. That is,it is possible to prevent resources from being wasted as caused in themapping method of FIG. 3.

To be more specific, in terminal 100, RF receiving section 105 is formedto be able to change a reception band, frame synchronization section 115obtains an SCH, which are placed in a predetermined frequency positionand then transmitted from base station 200 and which can be interpretedby an LTE terminal and LTE+ terminal, from a reception signal receivedin RF receiving section 105, and find synchronization with base station200, and RACH preamble section 145 transmits an RACH preamble to basestation 200 at the timing a preparation of RACH preamble transmission iscompleted. Then, control section 140 sequentially changes the receptionband of RF receiving section 105 and, after synchronizationestablishment and before RACH preamble transmission, prepares RACHpreamble transmission based on a P-BCH, PDCCH and D-BCH which can beinterpreted by the LTE terminal and the LTE+ terminal and which aretransmitted from base station 200 in the initial access unit bandincluding the synchronization channel frequency position. Further, afterRACH preamble transmission, control section 140 obtains report resourceallocation information reported by a PDCCH from base station 200,transmits terminal capability information of that terminal usingresources indicated by this report resource allocation information, and,based on a band moving indication transmitted in base station 200according to the terminal capability information, changes the receptionband from the initial access unit band.

Also, the band moving indication transmitted from base station 200includes information required to start data communication in thedestination unit band. To be more specific, the band moving indicationincludes the extension of PDCCH in the frequency axis direction, thenumber of antennas of the base station in the destination band (i.e.,the number of antennas to transmit a reference signal) and the number ofOFDM resources used for others than PDCCH's (e.g., a response signal toan uplink data signal).

By this means, even if terminal 100 is moved to a unit band on which aP-SCH, S-SCH, P-BCH and D-BCH are not mapped, terminal 100 can startdata communication without problems.

Also, according to the above mapping method, a D-BCH+ is necessarilymapped on the destination band of terminal 100. This D-BCH+ includesinformation required to continue communication in an LTE+ terminal.Therefore, terminal 100 can continue stable communication in thedestination unit band.

Also, although a case has been described above where terminal 100independently changes the RF center frequency and shifts to an idle modewhen sequential data communication with base station 200 is finished,the present invention is not limited to this, and, when sequential datacommunication between terminal 100 and base station 200 is finished,terminal 100 may be moved to the initial access unit band bytransmitting a band moving indication again from base station 200 toterminal 100.

Embodiment 2

In Embodiment 2, an LTE+ base station maps a reference signal, which canbe interpreted only by an LTE+ terminal, on a unit band different from aunit band on which an LTE broadcast signal and LTE dynamic broadcastsignal are mapped. Then, in the destination unit band, the LTE+ terminalmeasures the reception strength of the above reference signal andprepares for handover. Also, the basic configurations of the terminaland base station according to the present embodiment are the same as theconfigurations of the terminal and base station explained inEmbodiment 1. Therefore, the terminal according to the presentembodiment will be also explained using FIG. 4 and FIG. 5.

In base station 200 according to Embodiment 2, similar to Embodiment 1,OFDM signal forming section 225 maps a P-SCH, S-SCH, P-BCH and D-BCH,which can be interpreted by an LTE terminal and LTE+ terminal, on partof a plurality of unit bands that can be used by that base station, andmaps a D-BCH+ that can be interpreted only by the LTE+ terminal on allof the plurality of unit bands. Furthermore, OFDM signal forming section225 maps a reference signal that can be interpreted by the LTE+ terminalon a unit band different from the unit band on which the P-SCH, S-SCH,P-BCH and D-BCH are mapped. As this reference signal, specifically, asynchronization signal (P-SCH+, S-SCH+) that can be interpreted only bythe LTE+ terminal is used. That is, base station 200 according toEmbodiment 2 transmits a synchronization signal, broadcast signal andcontrol channel in the mapping method as shown in FIG. 8.

Also, in terminal 100 according to Embodiment 2, broadcast informationreceiving section 125 receives a reference signal transmitted from anLTE+ base station different from base station 200 that is the datacommunicating party in the destination unit band.

Then, a measurement section (not shown) provided in control section 140measures the reception strength of the reference signal received inbroadcast information receiving section 125.

Operations of terminal 100 having the above configuration will beexplained. FIG. 9 illustrates the operations of terminal 100 accordingto Embodiment 2. In FIG. 9, adjacent cells A and B have the samecommunication band.

Now, terminal 100 is moved to unit band 3 in cell B (which is a cell ofbase station 200) and then performs data communication. At this time, anLTE+ base station in cell A transmits a reference signal (P-SCH+,S-SCH+) in unit band 3. Therefore, terminal 100 can receive thereference signal (P-SCH+, S-SCH+) transmitted from adjacent cell A.Therefore, terminal 100 can measure the reception strength of thereference signal transmitted from adjacent cell A while performing datacommunication with base station 200. That is, it is possible tosimultaneously implement measurement processing for adjacent cell A andreception of downlink data from cell B, which are performed for handoverpreparation. By this means, the power consumption of terminal 100 isreduced.

Also, in a subframe (i.e., an area defined by a predetermined frequencybandwidth and predetermined time length), the number of symbols on whichthe reference signal (P-SCH+, S-SCH+) is mapped may be smaller than thenumber of symbols on which a P-SCH and S-SCH are mapped. In this case,information about the number of symbols on which the reference signal(P-SCH+, S-SCH+) is mapped in a subframe is shared between adjacent LTE+base stations. Then, to ease measurement processing of a referencesignal transmitted in the adjacent cell, base station 200 may explicitlyreport transmission position information (frequency, time) of thereference signal (P-SCH+, S-SCH+) in the adjacent cell to terminal 100or implicitly report the transmission position information by issuing anindication to perform measurement in the corresponding frequency at thetiming the adjacent cell transmits the reference signal.

Although example cases have been described above with Embodiments 1 to 4where the present invention is implemented with hardware, the presentinvention can be implemented with software.

Furthermore, each function block employed in the description of each ofEmbodiments 1 to 4 may typically be implemented as an LSI constituted byan integrated circuit. These may be individual chips or partially ortotally contained on a single chip. “LSI” is adopted here but this mayalso be referred to as “IC,” “system LSI,” “super LSI,” or “ultra LSI”depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be regenerated is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2008-201005, filed onAug. 4, 2008, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The base station, terminal, band assignment method and downlink datacommunication method of the present invention are useful to realize amethod of mapping a synchronization signal and broadcast signal havinghigh use efficiency of resources, in a case where there are a firstsystem in which single communication is independently assigned everyunit band having a predetermined bandwidth and a second system whichfollows the first system and in which a plurality of unit bands can beassigned in single communication.

The invention claimed is:
 1. A communication apparatus whichcommunicates with a user equipment on a plurality of component carriersin a first system, the first system being different from a second systemwhere another user equipment can communicate on a single componentcarrier of the plurality of component carriers, the communicationapparatus comprising: a generator which, in operation, generatesdirective information, the directive information being necessary for theuser equipment to receive a PDCCH (Physical Downlink Control Channel) ina second component carrier that is to be added to and is different froma first component carrier, the first component carrier being a componentcarrier in which synchronization is performed by the user equipment, andthe directive information including a downlink frequency bandwidth ofthe second component carrier, a number of antennas for use in the secondcomponent carrier, and resources used to transmit a response signal inthe second component carrier responsive to an uplink data signal; and atransmitter which, in operation, transmits the directive information tothe user equipment in the first component carrier on a PDSCH (PhysicalDownlink Shared Channel) and transmits the PDCCH to the user equipmentin the second component carrier after transmitting the directiveinformation.
 2. The communication apparatus according to claim 1,wherein, the second component carrier does not include a synchronizationsignal.
 3. The communication apparatus according to claim 1, wherein thefirst system is a LTE Advanced system, and the second system is a LTEsystem.
 4. The communication apparatus according to claim 1, wherein amaximum bandwidth supported in the first system is over 20 MHz, and amaximum bandwidth supported in the second system is 20 MHz.
 5. Thecommunication apparatus according to claim 1, wherein a maximumbandwidth of the plurality of component carriers is over 20 MHz, and amaximum bandwidth of the single component carriers is 20 MHz.
 6. Acommunication method of communicating with a user equipment on aplurality of component carriers in a first system, the first systembeing different from a second system where another user equipment cancommunicate on a single component carrier of the plurality of componentcarriers, the communication method comprising: generating directiveinformation, the directive information being necessary for the userequipment to receive a PDCCH (Physical Downlink Control Channel) in asecond component carrier that is to be added to and is different from afirst component carrier, the first component carrier being a componentcarrier in which synchronization is performed by the user equipment, andthe directive information including a downlink frequency bandwidth ofthe second component carrier, a number of antennas for use in the secondcomponent carrier, and resources used to transmit a response signal inthe second component carrier responsive to an uplink data signal; andtransmitting the directive information to the user equipment in thefirst component carrier on a PDSCH (Physical Downlink Shared Channel)and transmitting the PDCCH to the user equipment in the second componentcarrier after transmitting the directive information.
 7. Thecommunication method according to claim 6, wherein the second componentcarrier does not include a synchronization signal.
 8. The communicationmethod according to claim 6, wherein the first system is a LTE Advancedsystem, and the second system is a LTE system.
 9. The communicationmethod according to claim 6, wherein a maximum bandwidth supported inthe first system is over 20 MHz, and a maximum bandwidth supported inthe second system is 20 MHz.
 10. The communication method according toclaim 6, wherein a maximum bandwidth of the plurality of componentcarriers is over 20 MHz, and a maximum bandwidth of the single componentcarriers is 20 MHz.